WASHINGTON (Yonhap News) -- The late North Korean leader Kim Jong-il had been groomed from as early as 1974 to take over the helm of the communist nation from his father, a newly-disclosed diplomatic document showed Sunday.

It showed that Kim, who died on Dec. 17, had prepared for two decades to become the North’s leader, unlike his third son Jong-un, who became the crown prince just a few years ago.

According to a diplomatic cable by East Germany’s ambassador to Pyongyang, dated Nov. 12, 1974, quoting an “inner of circle friends” of North Korea, “Party meetings were held across the DPRK to swear loyalty to Kim Jong-il, the son of Kim Il-sung, in case something grave happened to Kim Il-sung.” The DPRK is the acronym of the North’s official name, the Democratic People’s Republic of Korea.

“The first large photos of Kim Il-sung’s eldest son have showed up in offices, featuring slogans of statements he made on reunification and socialist construction,” it added.

The Woodrow Wilson International Center for Scholars, a think tank in Washington, studied the dossier and made it public on its Web site as part of the North Korea International Documentation Project.

The center said, “While Kim Jong-il would not become Supreme Leader until July 1994, the succession process began so early.”

“Kim Jong-il’s rise to power thus extended over two decades, dwarfing the two to three years during which the ’great successor‘

Kim Jong-un, Kim Jong-il’s third and youngest son, has been vetted and prepared,” it pointed out.